Heated transfer line

Abstract

A flexible, foldable light-weight gas chromatography transfer line suitable for connecting a gas chromatograph (GC) to a spectrometer, such as a mass spectrometer or optical spectrometer, in particular to the ion source of the spectrometer, such as an inductively coupled plasma (ICP) ion source. The transfer line has a heating arrangement that allows maintaining an even temperature profile, which improves quality of spectra. The transfer line has low thermal mass and the heating can be controlled with the control unit of the GC.

The invention claimed is: 
     
       1. A flexible gas chromatography transfer line for transferring a sample from a gas chromatography column into a spectrometer for analysis, having an entry end for connecting to the gas chromatography column and an exit end for connecting with a spectrometer, the transfer line comprising:
 a flexible transfer capillary for receiving therein an end portion of a gas chromatography column or a capillary connected to said end portion; and 
 a flexible resistive heating arrangement, surrounding the transfer capillary; 
 the resistive heating arrangement being connectable to a power supply for providing current to the resistive heating arrangement to heat the resistive heating arrangement and thereby heat the flexible transfer capillary; 
 wherein the resistive heating arrangement is divided into at least one central zone and at least one exit zone, 
 wherein the resistive heating arrangement is adapted to provide different heat emission per unit length in said at least one central zone than in said exit zone, 
 wherein the flexible gas chromatography transfer line is foldable, a displacement force in each direction (x, y, z) needed to move the transfer line exit end when the entry end is fixed being less than 10 N. 
 
     
     
       2. The gas chromatography transfer line of  claim 1  wherein the resistive heating arrangement is divided into at least one central zone, at least one exit zone, and at least one entry zone. 
     
     
       3. A flexible gas chromatography transfer line for transferring a sample from a gas chromatography column into a spectrometer for analysis, having an entry end for connecting to the gas chromatography column and an exit end for connecting with a spectrometer, the transfer line comprising:
 a flexible transfer capillary for receiving therein an end portion of a gas chromatography column or a capillary connected to said end portion; and 
 a resistive heating arrangement, surrounding the transfer capillary, the resistive heating arrangement is divided into at least one central zone, at least one exit zone, and at least one entry zone, the resistive heating arrangement comprising resistive wire, wherein a pitch of the resistive wire in said central zone is in the range of about 5% to about 35% greater than the pitch in the at least one entry zone and the pitch in said at least one exit zone; 
 the resistive heating arrangement being connectable to a power supply for providing current to the resistive heating arrangement to heat the resistive heating arrangement and thereby heat the flexible transfer capillary; 
 wherein the resistive heating arrangement is divided into at least one central zone and at least one exit zone, 
 wherein the resistive heating arrangement is adapted to provide different heat emission per unit length in said at least one central zone than in said exit zone, 
 wherein the flexible gas chromatography transfer line is foldable, a displacement force in each direction (x, y, z) needed to move the transfer line exit end when the entry end is fixed being less than 10 N. 
 
     
     
       4. The gas chromatography transfer line of  claim 1 , wherein a thermal mass of the transfer line is in the range of about 5 to about 50 J/K. 
     
     
       5. The gas chromatography transfer line of  claim 1 , wherein the resistive heating arrangement comprises a resistive heating layer. 
     
     
       6. The gas chromatography transfer line of  claim 5 , wherein the resistive heating layer comprises a carrier sheet comprising electrically resistive material. 
     
     
       7. The gas chromatography transfer line of  claim 1 , wherein the resistive heating arrangement comprises a resistive wire, wherein the resistive wire comprises at least two exit zones, a first exit zone more distal from the central zone and a second exit zone more proximal to the central zone, wherein: (i) a pitch of the wire in said first exit zone is smaller than a pitch in said second exit zone, which is smaller than a pitch in the central zone, or (ii) a resistance of the wire in said first exit zone is higher than a resistance of the wire in said second exit zone, which in turn is higher than a resistance of the wire in the central zone, or (iii) a winding pattern of the wire in said first exit zone is different to a winding pattern of the wire in said second exit zone, which in turn is different to a winding pattern of the wire in the central zone. 
     
     
       8. The gas chromatography transfer line of  claim 1 , wherein said exit end is adapted to pass through a gas-tight rubber or polymer seal of a connector adapted to connect the transfer line to a mass spectrometer sample injector and/or ICP ion source. 
     
     
       9. The gas chromatography transfer line of  claim 1 , wherein the flexible transfer capillary comprises a metal tubing with an inert coating on an inner surface. 
     
     
       10. The gas chromatography transfer line of  claim 9 , wherein the inert coating is selected from silicon based coatings, other glassy coatings, and polymer coatings. 
     
     
       11. The gas chromatography transfer line of  claim 1 , wherein the flexible transfer capillary is adapted to receive a GC column such that the GC column terminates within heated zones of the flexible transfer capillary. 
     
     
       12. The gas chromatography transfer line of  claim 1 , wherein the flexible transfer capillary is adapted to connect at or near the entry end to a supply of inert carrier gas such that the carrier gas can flow in a space between the transfer capillary and a GC column in a direction towards the exit end of the transfer capillary. 
     
     
       13. The gas chromatography transfer line of  claim 1 , wherein the resistive heating arrangement terminates at a predetermined distance from the entry end of the transfer line so that, during operation, a part of the transfer capillary that is not enclosed by the heating arrangement is positioned within an oven of a gas chromatograph to which the transfer line is connected. 
     
     
       14. The gas chromatography transfer line of  claim 1 , wherein the flexible transfer capillary has an inner diameter in the range of about 0.40 mm to about 1.0 mm and an outer diameter in the range of about 1.0 mm to about 2.5 mm. 
     
     
       15. A flexible gas chromatography transfer line for transferring a sample from a gas chromatography column into a spectrometer for analysis, having an entry end for connecting to the gas chromatography column and an exit end for connecting with a spectrometer, the transfer line comprising:
 a flexible transfer capillary for receiving therein an end portion of a gas chromatography column or a capillary connected to said end portion; 
 a resistive heating arrangement, surrounding the transfer capillary; and 
 an outer heat insulating sleeve along at least a portion thereof; 
 the resistive heating arrangement being connectable to a power supply for providing current to the resistive heating arrangement to heat the resistive heating arrangement and thereby heat the flexible transfer capillary; 
 wherein the resistive heating arrangement is divided into at least one central zone and at least one exit zone, 
 wherein the resistive heating arrangement is adapted to provide different heat emission per unit length in said at least one central zone than in said exit zone, 
 wherein the flexible gas chromatography transfer line is foldable, a displacement force in each direction (x, y, z) needed to move the transfer line exit end when the entry end is fixed being less than 10 N. 
 
     
     
       16. The gas chromatography transfer line of  claim 1 , further comprising at least one temperature sensor to provide feedback to a temperature control unit. 
     
     
       17. The gas chromatography transfer line of  claim 16 , wherein the temperature control unit is interfaced to a power supply to control an output of the power supply to the resistive heating arrangement and thereby control a temperature of the flexible transfer capillary. 
     
     
       18. The gas chromatography transfer line of  claim 1 , wherein the transfer line and a temperature controller to which it is connected are adapted to ramp the temperature of the transfer line at a rate that is in the range of about 10° C./min to about 200° C./min. 
     
     
       19. The gas chromatography transfer line of  claim 18 , wherein the transfer line can be heated to and maintained at a temperature within a temperature range comprising at least the range from about 100° C. to about 350° C. 
     
     
       20. The gas chromatography transfer line of  claim 1 , wherein the transfer line has a bending radius of less than about 40 mm. 
     
     
       21. The gas chromatography transfer line of  claim 1 , wherein the transfer line has an outer diameter in the range of about 2 to about 10 mm. 
     
     
       22. The gas chromatography transfer line of  claim 1 , wherein the transfer line has a weight of less than about 100 g. 
     
     
       23. The gas chromatography transfer line of  claim 1 , wherein the transfer line is adapted to connect at the entry end to a gas chromatography column and at the exit end to an inductively coupled plasma (ICP) ion source. 
     
     
       24. The gas chromatography transfer line of  claim 1 , wherein the transfer line has a thermal mass per unit length in the range of about 5 to 30 J/K·m. 
     
     
       25. The gas chromatography transfer line of  claim 1 , wherein the transfer line has a specific heat capacity in the range of about 100 to 500 J/(kg·K).